Download our flat bottom boat design for the extreme flats 20, a light weight, quiet hull with low freeboard. buy flats boat plans and more at bateau.com!. Boat plans catalog – 300 boats you one response to flats flyer design. latest photos | boatbuilders site on glen-l.com says: november 8, 2013 at 9:34 am. Spira international wooden boat plans. following are the stock plans available for the various types of boats, separated into the different categories..